Western Maryland is restoring a compound articulated, number 1306.( or is it 1308?) I have no ETA on this one.
Norfolk and Western Class "J" 611 will be in steam this spring/early summer.
The New Mexico Steam Locomotive & RHS is restoring Santa Fe 4-8-4 Northern 2926. Getting ready to stuff flues in her belly. Should see a fire in the firebox sometime this summer.
UP has no operating steam and it looks like that may continue through 2015. I doubt if we see 4014 in steam by 2020.
There's probably some smaller players under restoration, but these are the big hitters I can tell you about.